Scope & why this matters

Substance- or medication-induced disorders include a wide range of presentations — acute psychosis, mood disturbance, neurocognitive impairment, movement disorders, seizures and autonomic instability. Novel psychoactive substances (NPS) and polypharmacy increase diagnostic uncertainty. Early recognition and syndrome-directed care reduce morbidity and mortality.

Typical clinical presentations

• Acute psychosis: hallucinations, delusions, severe agitation.
• Mood syndromes: mania-like excitation or severe depression.
• Neurocognitive impairment: delirium, confusion, memory disturbance.
• Movement disorders: dystonia, akathisia, parkinsonism, chorea.
• Neurological emergencies: seizures, status epilepticus, malignant hyperthermia-like syndromes.
• Autonomic dysfunction: hyperthermia, tachycardia, labile blood pressure, diaphoresis.

Assessment — immediate priorities

1. Stabilise ABCs: airway protection, oxygen, ventilation and circulation.
2. Rapid observation: GCS, vital signs, temperature, pupils, skin, neuromotor exam.
3. Rule out primary medical causes (hypoglycaemia, hypoxia, intracranial events) and delirium.
4. Obtain collateral history and witness accounts where possible; look for paraphernalia or medication packaging.
5. Medication reconciliation including prescribed, OTC, herbal and recent changes.

Investigations — immediate & targeted

• Immediate: capillary glucose, ECG, pulse oximetry, ABG if respiratory compromise suspected.
• Blood: CBC, electrolytes, renal & liver function, CK, coagulation, serum osmolality, blood alcohol level.
• Toxicology: urine drug screen and serum assays where available — interpret clinically (many agents not detected).
• Neuroimaging: CT head for trauma or focal neurological signs; MRI when safe and indicated.
• EEG for unexplained altered consciousness or suspected non-convulsive seizures.

Management principles — syndrome-based

1. Prioritise safety: control agitation, prevent injury, maintain thermoregulation and treat seizures promptly.
2. Syndrome-directed treatments: use antidotes when strongly indicated (naloxone for opioids, flumazenil rarely), benzodiazepines for sedative-withdrawal and stimulant agitation, antipsychotics cautiously for psychosis.
3. Supportive care: fluids, electrolyte correction, oxygen, cooling for hyperthermia, monitoring in high-dependency settings if unstable.
4. Avoid harm: be cautious with polypharmacy — e.g., avoid combining large sedative doses with respiratory depressants.
5. Escalation: involve ICU, neurology or toxicology early for complex or refractory cases.

Specific management notes

Acute psychosis & severe agitation

• Non-pharmacological de-escalation first: calm environment, verbal reassurance and distancing triggers.
• If required, use short-acting antipsychotics (olanzapine IM/oral, quetiapine oral) or haloperidol with caution — monitor for extrapyramidal symptoms and QTc prolongation.
• Benzodiazepines (lorazepam) can be effective for stimulant-induced agitation but monitor respiratory function if sedatives co-ingested.

Delirium and severe cognitive disturbance

• Identify and treat underlying medical causes; use low-dose antipsychotics for severe distress or risk — avoid in Parkinsonian presentations or when LBD suspected.
• Optimize environment (reorientation, sleep/wake cycle, family presence) and review all medications.

Seizures and status epilepticus

• Treat with benzodiazepines immediately (lorazepam IV), followed by second-line agents (levetiracetam, valproate, phenytoin) per local protocols.
• Arrange EEG and critical care escalation for refractory status.

Serotonin syndrome vs anticholinergic toxicity

• Differentiate clinically: serotonin syndrome features hyperreflexia and clonus; anticholinergic toxicity has dry skin, mydriasis and reduced bowel sounds.
• Treat serotonin syndrome with benzodiazepines, aggressive cooling and cyproheptadine if indicated; consider physostigmine for severe anticholinergic toxicity in specialist settings.

Movement disorders (acute dystonia / akathisia)

• Acute dystonia: give IV/IM or oral anticholinergic (e.g., procyclidine) or benztropine; consider benzodiazepines if needed.
• Akathisia: beta-blockers (propranolol) or anticholinergics and lower offending drug where possible.

Disposition & follow-up

• Admit to appropriate level of care based on stability: observation unit, medical ward, high-dependency or ICU.
• Document capacity and obtain consent where possible; involve substitute decision-makers if capacity impaired.
• On recovery, provide brief intervention, harm-reduction advice, naloxone kits where relevant and prompt referral to addiction services for ongoing care.
• Arrange outpatient follow-up with psychiatry, neurology or toxicology as indicated; consider neuropsychology if cognitive deficits persist.

Key takeaways

• Treat the syndrome, not the label — use clinical features to direct immediate care when the causative agent is unknown.
• Prioritise airway, breathing and circulation; control agitation and seizures promptly.
• Use antidotes when indicated, but avoid empiric treatments that may harm (e.g., flumazenil in chronic benzodiazepine users).
• Provide harm reduction, linkage to addiction services and clear documentation for safe follow-up.